Population-based study of effect of surgery versus chemotherapy in pancreatic cancer patients in Denmark

A hypothetical randomized trial based on data in Danish healthcare registries 2008-2021) estimated the causal effect of surgery versus chemotherapy on survival in patients with T1-3NxM0 pancreatic cancer. At the time of diagnosis, data of each patient were duplicated; one copy was assigned to the surgery protocol and one copy to the chemotherapy protocol of the hypothetical trial. Copies were censored when the assigned treatment deviated from the observed treatment. To account for informative censoring, uncensored patients were weighted according to confounders. The 3-year overall survival was 39.7% (95% CI 36.7-42.6) after surgery and 22.7% (17.7-28.4) after chemotherapy, corresponding to an absolute difference of 17.0% (10.8-23.1). In conventional survival analysis using propensity score-based inverse probability weighting, this difference was 23.0% (95% CI 17.0-29.0). The authors conclude that surgery was superior to chemotherapy in achieving long-term survival for pancreatic cancer. The difference comparing surgery and chemotherapy was substantially smaller when using the clone-sensor-weight approach than conventional survival analysis.